1. Field of the Invention
The present invention relates to a scanning apparatus which performs scan on an object with a charged particle beam, a drawing apparatus which includes the scanning apparatus and performs drawing on a substrate, and a method of manufacturing an article using the drawing apparatus.
2. Description of the Related Art
A charged particle beam irradiation apparatus blanks a charged particle beam, emitted by a charged-particle source, in accordance with drawing data while making a deflector scan the charged particle beam to irradiate a predetermined position on a sample with a predetermined amount of charged particle beam. A charged particle beam drawing apparatus blanks a charged particle beam, emitted by a charged-particle source, in accordance with drawing data while making a deflector scan the charged particle beam to irradiate a predetermined position on a substrate with a predetermined amount of charged particle beam, thereby drawing a circuit pattern on the substrate. The blanking is an operation of switching between ON and OFF of the irradiation of the substrate with a charged particle beam. Controlling the timing of this switching operation makes it possible to control the time taken to irradiate a unit region with a charged particle beam. Also, the deflector can change the deflection amount of a charged particle beam by controlling a voltage applied across the electrodes. The drawing data is circuit pattern bitmap data generated from CAD data of circuit design. The charged particle beam drawing apparatus performs drawing in accordance with the drawing data, and therefore requires no circuit pattern mask used in the conventional exposure apparatus. Hence, various developments are in progress in order to reduce the running cost intended for a miniaturization process of increasing the mask cost, and limited production of a wide variety of products which require a large number of masks. The current mainstream charged particle beam drawing apparatus is an electron-beam exposure apparatus which uses an electron beam. An electron-beam exposure apparatus will be taken as an example hereinafter.
The electron-beam exposure apparatus performs drawing while scanning an electron beam, and therefore has a low throughput. Hence, to improve the throughput, a method of drawing by simultaneously using a large number of electron beams has been proposed. In this case, it is possible to set a deflector for each electron beam to control its deflection amount. However, deflector electrodes, electrode driving circuits, applied voltage command circuits, and wiring lines which connect them to each other are required in numbers equal to the number of electron beams, entailing a high cost. Also, the requirement of a large number of circuits increases the probability that a failure will occur, thus increasing the maintenance load. For this reason, a method of guiding electron beams between the electrodes of one deflector to collectively deflect them is used.
When electron beams are collectively deflected using one deflector, it is desired to deflect all electron beams in the same amount in the same direction. However, the deflection amount is different for each electron beam if the electric field produced between the deflector electrodes is not uniform. In such a case, because the applied voltage cannot be adjusted individually for each electron beam, International Publication No. 2010/134018 discloses a method of expanding/contracting drawing data in accordance with the deflection amount of each electron beam to draw a pattern at a desired position on a substrate. Also, because an error occurs in the relationship between the applied voltage and the deflection amount of each electron beam due, for example, to nonuniformity of the electric field between the deflector electrodes, Japanese Patent No. 4074240 proposes a method of correcting the applied voltage in accordance with the deflection amount using a minimum amount of data to obtain a desired deflection amount.
A more uniform electric field can be produced when the electrodes used in the deflector are larger and are more sufficiently spaced apart from the region through which each electron beam passes. However, the use of such electrodes increases the size and cost of the deflector. Under the circumstances, the electric field between the deflector electrodes is not uniform and considerably varies not only in strength but also in direction especially near the ends of the electrodes. Therefore, electron beams which pass near the ends of the electrodes generate errors not only in the amount of deflection but also in the deflection direction with respect to desired values. In International Publication No. 2010/134018, drawing data is expanded/contracted for each electron beam to draw a predetermined pattern even if an error occurs in the deflection amount, but an error of the deflection direction is not corrected. Also, International Publication No. 2010/134018 describes neither an obtaining method nor a holding method for correction data indicating the amount of expansion/contraction of drawing data. Also, as the number of electron beams increases to improve the throughput, it becomes more difficult to correct errors for each electron beam. More specifically, since an enormous amount of correction data is set for each electron beam, the cost for holding data using, for example, a memory increases. Also, the measurement time for obtaining correction data, and the update time of the correction data become considerable.
In Japanese Patent No. 4074240, in one electron beam, correction data is set for each region having a size that changes depending on the deflection amount, thereby reducing the required amount of correction data. However, it is necessary to provide correction data corresponding to a plurality of regions for each electron beam. Accordingly, with an increase in number of electron beams, the amount of correction data, the measurement time for obtaining correction data, and the update time of the correction data become considerable as well.